Proteomic Basis of the Antibody Response to Monkeypox Virus Infection Examined in Cynomolgus Macaques and a Comparison to Human Smallpox Vaccination

Abstract

Monkeypox is a zoonotic viral disease that occurs primarily in Central and West Africa. A recent outbreak in the United States heightened public health concerns for susceptible human populations. Vaccinating with vaccinia virus to prevent smallpox is also effective for monkeypox due to a high degree of sequence conservation. Yet, the identity of antigens within the monkeypox virus proteome contributing to immune responses has not been described in detail. We compared antibody responses to monkeypox virus infection and human smallpox vaccination by using a protein microarray covering 92–95% (166–192 proteins) of representative proteomes from monkeypox viral clades of Central and West Africa, including 92% coverage (250 proteins) of the vaccinia virus proteome as a reference orthopox vaccine. All viral gene clones were verified by sequencing and purified recombinant proteins were used to construct the microarray. Serum IgG of cynomolgus macaques that recovered from monkeypox recognized at least 23 separate proteins within the orthopox proteome, while only 14 of these proteins were recognized by IgG from vaccinated humans. There were 12 of 14 antigens detected by sera of human vaccinees that were also recognized by IgG from convalescent macaques. The greatest level of IgG binding for macaques occurred with the structural proteins F13L and A33R, and the membrane scaffold protein D13L. Significant IgM responses directed towards A44R, F13L and A33R of monkeypox virus were detected before onset of clinical symptoms in macaques. Thus, antibodies from vaccination recognized a small number of proteins shared with pathogenic virus strains, while recovery from infection also involved humoral responses to antigens uniquely recognized within the monkeypox virus proteome.

Humoral Immunity to Smallpox Vaccines and Monkeypox Virus Challenge: Proteomic Assessment and Clinical Correlations

“…The protein was recognized only weakly in one human vaccinee and was previously seen with equivocal recognition by humans and no recognition by primate vaccinees (40,59). In comparison, strong recognition of E3 was seen in mice and rabbits given the pathogenic VACV WR strain (40,45), and primates challenged with MPXV show reactivity to E3, and in particular the truncated MPXV homologue of E3 (59). Similar to the absence of reactivity to A17, reactivity to E3 after vaccination may result from species-specific sensitivity to available epitopes, and only upon challenge (VACV WR or MPXV) is the response sufficient to ensure that it is measurable.…”

“…Although the limited number of immunodominant antigens after vaccination may have been expected to continue dominating the profile, along with the addition of a few novel targets that may have been recognized during vaccination but failed to generate a detectable antibody response, the large increase here suggests that differences in virus pathogenicities or life cycles affect immune recognition. It was observed that pathogenic WR virus infection of naïve rabbits induced a large and robust response to a broad range of proteins compared to vaccination alone (44), and a recent report showed that the antibody response to monkeypox virus infection of naïve macaques also targeted a larger number of antigens than human vaccination (59). Thus, dramatic increases in the frequency and intensity of responses to multiple targets upon challenge, but not repeat vaccination, provides evidence that increased pathogenicity drives the stronger immune response.…”

Assessment of the Protective Effect of Imvamune and Acam2000 Vaccines against Aerosolized Monkeypox Virus in Cynomolgus Macaques

“…Thus, a well-defined animal model using monkeypox virus should mimic the natural course of smallpox disease. Macaques have been used at various stages of smallpox vaccine and antiviral research (16,(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36), and in each case the route of infection, dose, and choice of challenge strain have been key factors in determining whether the macaque model of monkeypox resembles human clinical variola virus infection.…”

Characterizing monkeypox virus specific CD8+ T cell epitopes in rhesus macaques

“…Macaques infected with MPXV generate both neutralizing antibodies [7,12] and T cell responses [13]. Upon proteomic array analysis, while antibodies from MPXV-infected macaques and vaccinia-vaccinated humans recognized a few common proteins, antibodies from MPXV-infected macaques also recognized proteins that were not recognized by vaccinated human sera [12]. It is interesting to determine if this also applies to T cell responses.…”